A Department of Commerce review of steep import duties imposed on photovoltaic (PV) panels made in China may result in sharply lower tariffs, but U.S. consumers aren’t likely to see much benefit, .

The International Trade Administration, part of the Commerce Department, suggested in a preliminary report on Jan. 2 that the 2012 anti-dumping and countervailing duties should be reduced from a combined 31 percent to 18 percent, Bloomberg said.

Installers such as SolarCity Corp. and Vivint Solar Inc. should see a “substantial potential improvement to U.S. margins,” Bloomberg said, but homeowners won’t get much of a boost because the cost of PV panels is less than a third of total installation costs. “Soft costs” such as permitting, finance, and design account for the lion’s share of the cost of a residential PV system.

Bloomberg quoted Shayle Kann, an analyst with GTM Research, as saying a final determination probably won’t be made until May or June.

The long-running trade squabble began with a request from SolarWorld, a German company with a panel factory in Oregon, that the U.S. government impose import tariffs on Chinese-made PV panels.

But the dispute is complex, in part because U.S. companies are among suppliers of the polysilicon used to manufacture the panels. Just last month, a U.S. semiconductor manufacturer said it would close a $1.2 billion polysilicon factory that it finished just two years ago in Tennessee, , because polysilicon prices collapsed — one of the fallouts of the trade dispute.